[#321] Validate All Project Identifier Arguments

* Fix a bug where project identifiers were not validated for the
  `issues` and `watched` commands.

Closes #321: Project Identifiers are not Validated for the Issues
Command
[#315] Remove Bug Tracker Link in Error Messages

* Remove the "Please report bugs to..." message and the link to the bug
  tracker that followed any error messages.

Closes #315: Remove Debugging Output